Method to build a wirebond probe card in a many at a time fashion

ABSTRACT

Resilient spring contacts for use in wafer test probing are provided that can be manufactured with a very fine pitch spacing and precisely located on a support substrate. The resilient contact structures are adapted for wire bonding to an electrical circuit on a space transformer substrate. The support substrates with attached spring contacts can be manufactured together in large numbers and diced up and tested before attachment to a space transformer substrate to improve yield. The resilient spring contacts are manufactured using photolithographic techniques to form the contacts on a release layer, before the spring contacts are epoxied to the support substrate and the release layer removed. The support substrate can be transparent to allow alignment of the contacts and testing of optical components beneath. The support substrate can include a ground plane provided beneath the spring contacts for improved impedance matching.

BACKGROUND

1. Technical Field

The present invention relates to a resilient electrical contact element,or spring contact for making pressure contacts between electricalcomponents, and more particularly to spring contacts and a structure forattachment of the spring contacts to a substrate to form a probe cardfor use in probing to test integrated circuits (ICs) on a wafer.

2. Related Art

Resilient contact elements, or spring contacts are manufactured in avariety of forms. One type of spring contacts used for probing ICs on awafer is described in U.S. Pat. No. 5,476,211 entitled “Method ofManufacturing Electrical Contacts, Using a Sacrificial Member” and itscounterpart divisional patents, U.S. Pat. Nos. 5,852,871, and 6,049,976,all by Khandros. These patents disclose methods for making resilientinterconnection elements by mounting a flexible elongate core element(e.g., wire “stem” or “skeleton”) to a terminal on an electroniccomponent and coating the flexible core element with a “shell” of one ormore materials to ensure the resilient nature of resulting springcontacts. Exemplary materials for the core element include gold.Exemplary materials for the resilient coating include nickel and itsalloys. The resulting spring contact element is used to make pressureconnections between two or more electronic components including betweena probe card and integrated circuits on a wafer.

Connection of the spring contacts to a substrate to form a probe card,or other structure with spring contacts is described in U.S. Pat. No.5,974,662, entitled “method of Planarizing Tips of Probe Elements of aProbe Card Assembly” by Eldridge, Grube, Khandros and Mathieu. Thispatent describes a probe card assembly, including a substrate withelongate resilient spring contact elements mounted to form a “spacetransformer.” A space transformer is a multilayer interconnectionsubstrate having terminals disposed at a first pitch, or spacing betweenterminals, on a one surface and having corresponding terminals disposedat a second pitch on an opposite surface. Space transformation isprovided by routing lines in the layers of the substrate used to effect“pitch-spreading” from the first pitch to the second pitch. In use, thefree ends (tips) of the elongate spring contact elements make pressureconnections with corresponding terminals on an electronic componentbeing probed or tested.

Another type of spring contact elements is described in U.S. Pat. No.6,482,013, entitled “Microelectronic Spring Contact Element andElectronic Component Having A Plurality Of Spring Contact Elements” byEldridge, Grube, Khandros and Mathieu, incorporated herein by reference.This patent describes photo lithographic rather than mechanicaltechniques to fabricate resilient contact elements. As with themechanically formed contact elements, the resilient contact elementsformed using lithographic techniques include a resilient material, suchas nickel and its alloys. To manufacture a probe card, or othersubstrate with resilient contacts using photolithographic techniques,the spring contacts are formed on metal interconnect pads on the surfaceof the substrate by a series of steps including plating or deposition ofmaterial, applying photoresist, masking using photolithographictechniques, and etching. For a space transformer, the interconnect padson which the resilient contacts are formed connect the resilientcontacts to routing lines within the space transformer substrate. Usingphotographic techniques, close tolerances can be realized to assurealignment of the spring contacts formed thereon with correspondingcontact pads on an integrated circuit being tested.

SUMMARY

In accordance with the present invention, resilient contact structuresare described that can be manufactured with a very fine pitch andprecisely located on a support substrate. The resilient contactstructures are adapted for wire bonding on one end to make electricalcontact with a circuit, while providing a spring contact on another end.Support substrates with these spring contacts can be made in a many at atime fashion, reducing manufacturing costs, and providing redundancy toincrease manufacturing yield.

The resilient contact structure in accordance with the present inventionis made using photolithographic techniques. The resilient contactstructure is formed on a release layer of a sacrificial substrate, andthen affixed by an adhesive material to the support substrate before thesacrificial substrate is removed. The support substrate now supportingthe resilient contact structures is then attached to a base substratethat includes transmission lines. The base substrate can be directlyattached using an adhesive. As an alternative, the base substrate isattached by resilient springs so that the support substrate provides acompliant platform.

Transmission lines of the base substrate in one embodiment are attachedby wire bonding to the resilient contacts. In another embodiment whensprings are used to create the compliant platform, flexible conductiveleads are used to connect the resilient contacts to the base substrate.With the transmission lines of the base substrate routing signals fromthe resilient contacts on one surface to a finer pitch set of contacts,it can form a “space transformer” substrate typically used in waferprobing. For convenience, the base substrate is subsequently referred toas a space transformer substrate.

In one embodiment, the support substrate has a metal coating forming aground plane provided beneath the attached resilient contact structures.The adhesive attaching the resilient contact structures to the supportsubstrate is then a non-conductive material, such as epoxy, toelectrically isolate the contact structures from the ground plane. Theground plane then provides for better impedance matching through theresilient contact structure and wire bonds that connect to lines of thespace transformer substrate.

In a further embodiment, the support substrate is made of a transparentdielectric material, such as glass. By being transparent, alignment forattachment of the support substrate to the space transformer substratecan be easily performed to assure the resilient spring contacts willalign with contacts on another device, such as a wafer to be tested.Further with a transparent substrate, a light source can be providedthrough the substrate to test light sensitive components.

In a further embodiment, conductive vias are provided through thesupport substrate. The vias in one embodiment include solder bumps onone side for attaching to traces on the space transformer substrate.Other connection mechanisms than solder bumps, such as conductive epoxy,or otherwise, can be used to attach the vias to traces on the spacetransformer substrate. The resilient contact elements are wire bonded ontraces connecting to the vias, or directly on the vias on the opposingside of the support substrate. With a ground plane used on the supportsubstrate, isolation is provided between the signal line vias and theground plane region on the support substrate. The ground plane canfurther be connected by a via to a ground line of the space transformersubstrate.

In an additional embodiment, the resilient contact elements are formedin groups on a single support substrate, and after manufacture thesupport substrate is diced up into individual tiles for bonding to oneor more of the space transformer substrate. The tiles can include springcontacts arranged for testing ICs on a single device under test (DUT),or multiple DUTs. After attaching the tiles to the space transformersubstrate, wire bonding or another scheme to attach wires is performedto electrically connect the resilient contact elements to transmissionlines on the space transformer substrate. Dicing of the supportsubstrate enables tiles with defective contacts to be discarded, whilenon-defective tiles are used, increasing manufacturing yield.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the present invention are explained with the help ofthe attached drawings in which:

FIGS. 1A-1P are cross sectional views showing manufacturing steps forresilient contact elements provided on a support substrate in accordancewith the present invention;

FIG. 2 is a cross sectional view of resilient contact structures on asupport structure, with the support structure attached to a spacetransformer substrate and wire bonds provided from both contact elementsand a ground plane to contacts on the space transformer substrate;

FIG. 3 is a cross sectional view of resilient contact structures on asupport structure, with the support substrate including vias attached bysolder bumps to routing lines in a space transformer substrate, and wirebonds provided from the resilient contact structures to the vias;

FIG. 4 is a cross sectional view, with the support substrate attached tothe PCB by resilient springs forming a compliant platform for probing awafer;

FIG. 5 shows modification to the compliant platform configuration ofFIG. 4 so that the resilient contact structures are connected byflexible leads directly to the PCB without the need of separate wirebonding;

FIG. 6 is a cross sectional view showing resilient contact structures ona transparent support structure attached to a PCB to enable waferprobing, the PCB having openings allowing light to pass through thetransparent support to enable testing of light sensitive devices;

FIG. 7 shows a top view of resilient contact structures on the supportsubstrate, as configured to contact one configuration of pads on a DUT,with wire bonding of resilient contact structures as illustrated in FIG.2;

FIG. 8 shows a top view of resilient contact structures on the supportsubstrate alternatively having vias for connecting to the spacetransformer substrate, with wire bonding of resilient contact structuresto the vias as illustrated in FIG. 3;

FIG. 9 shows a resilient contact with wire bonding to a bond pad,similar to FIG. 8, but with a traces wire bonded in-between;

FIG. 10 shows a resilient contact with wire bonding through a trace to abond pad, similar to FIG. 9, but with the bond pad connected by a traceto a via;

FIG. 11 shows a top view of an alternative configuration of resilientcontact structures, as set to contact a different configuration of DUTpads than the configuration shown in FIGS. 7 and 8;

FIG. 12 shows a top view of a substrate on which resilient contactstructures are formed, illustrating how the substrate can be diced up toimprove manufacturing yield; and

FIG. 13 shows a cross sectional view of components of a probe cardillustrating flexible mounting of a space transformer substrate, as analternative to FIGS. 4-5.

DETAILED DESCRIPTION

FIGS. 1A-1P illustrate showing manufacturing steps for resilient contactelements provided on a tile substrate in accordance with the presentinvention. The present invention is not limited to the manufacturingsteps shown.

As illustrated in FIG. 1A, the process commences with a suitablesacrificial substrate 102, such as a silicon wafer. The sacrificialsubstrate 102 can further be composed of a material, such as aluminum,copper, ceramic, titanium-tungsten, and the like. On the sacrificialsubstrate, a blanket layer 105 of etch stop material, such as siliconnitride or silicon dioxide, is applied. A layer of masking material 104,such as photoresist, is then applied over the etch stop material 105.The masking material 104 is then imaged and developed usingphotolithographic techniques to expose areas 106 of the etch stopmaterial 105 over the sacrificial substrate 102. Alternatively selectedportions of the photoresist 104 can be removed employing othertechniques, such as known techniques involving lasers, and the resultingexposed portions of the masking layer 104 can be removed using chemicaletching processes, the result of which is that openings 106 in thephotoresist 104 to the surface of the etch stop material 105 arecreated.

In a subsequent step, illustrated in FIG. 1B, the exposed etch stopmaterial 105 is etched with an etchant, such as hydrofluoric acid (HF)to expose the substrate 102 in openings 106. The remaining photoresistmaterial 104 is then removed leaving etch stop material 105 over areasof the substrate 102 other than the openings 106.

In a subsequent step, illustrated in FIG. 1C, the sacrificial substrate102 is etched in the openings 106, using known chemistry for selectivelyetching the substrate. For example, a silicon substrate can selectivelybe etched using potassium hydroxide (KOH). This will create a smallgeometric intrusion (depression or trench) 110 in the substrate 102, thedepth of which is controlled by etch timing to correspond to a desireddepth for the intrusion. Also, in the case of employing a silicon waferas the sacrificial substrate 102, the sidewall 112 of the intrusion 110will be an angle other than vertical. As will be evident in thedescription to follow, the intrusion or trench 110 will define atopological feature present on the tip of a resilient contact structure(pyramid, truncated pyramid, etc.) In addition to being formed byetching using potassium hydroxide, the intrusion can also be formed bydimpling a metal substrate, dry etching as by reactive ion etching, orother procedures known in the art.

After creating the intrusions 110, the etch stop material 105 ispreferably removed, as illustrated in cross section in FIG. 1D. FIG.1D-1 shows a top view of the sacrificial substrate 102, shown in crosssection in FIG. 1D, with intrusions 110.

In a next step illustrated in FIG. 1E, an additional layer ofphotoresist 120 is applied and patterned using photolithographictechniques, leaving photoresist areas adjacent intrusions 110 exposed.The photoresist 120 may further optionally be slumped or shaped as shownin FIG. 1F, in area 122. The slumping 122 is performed by heating of thephotoresist. Shaping may be done by angular exposure of the photoresistmaterial 120 in the area 122, and then subsequent etching. The slumpedarea forms a mold for a bend in a resilient contact structure. Slumpingor shaping makes it easier to metalize the surface of the photoresist bysputtering. Alternatively, the cross section of FIG. 1F may be made byapplying an etch stop material, such as silicon dioxide or siliconnitride, and then etching as described in U.S. Pat. No. 6,482,013referenced previously.

In a next step illustrated in FIG. 1G, one or more metallic layers 130are blanket deposited, such as by sputtering, onto the substrate 102. Inone embodiment, the metallic layer is composed of two materials, thefirst material, such as aluminum, being selected as a release layer, anda second layer serving as a “seed” layer for deposition of subsequentlayers. As an example, the metallic layer 130 may be composed of arelease layer of aluminum followed by a seed layer of copper. Therelease material permits the sacrificial substrate to be removed afterthe spring contact elements fabricated thereon (as described herein) aremounted to a support substrate. The release material may be removed fromthe final spring contact after acting as a protective “capping” layerduring the release process.

Next, as illustrated in FIG. 1H, an additional masking layer 132, suchas photoresist, is applied to the substrate 102. The photoresist 132 ispatterned to define openings effectively forming a mold defining lengthsand widths desired for a resulting spring contact elements.

The resilient contact structures 140 are then formed by applying a layerof metal between the photoresist regions 132, as illustrated in FIG. 1Ito form resilient contacts. The relatively thick “structural” metalliclayer deposited between photoresist regions 132, is applied using asuitable process such as electroplating of a resilient material, such asnickel, as set forth previously, atop the release layer 130. As analternative to electroplating, techniques such as chemical vapordeposition (CVD), physical vapor deposition (PVD), or other techniquesavailable in the art could be used to apply the metal forming theresilient contact structures 140.

The metal layer described as forming the resilient contact structures140 is intended to control or dominate the mechanical characteristics ofthe resulting spring contact element. It is within the scope of thisinvention that additional layers may be included in the build-up of theresilient contact structure. For example, prior to depositing theresilient material such as nickel, a layer of a material selected forits superior electrical characteristics of electrical conductivity, lowcontact resistance, solderability, and resistance to corrosion may bedeposited. For example, gold or rhodium, (both of which are good contactmaterials), nickel-cobalt (a good material for brazing). In oneembodiment, prior to depositing the resilient material, a material isapplied which is suitable for wire bonding, such as gold, aluminum,palladium cobalt, etc.

Once formed, the contact structures 140 and photoresist material 132 canoptionally be lapped flat, as illustrated in FIG. 1J. With springbehavior being a function of thickness of the spring contact, lappingallows for a more precise control of the spring constant. The contactstructures 140 can be flattened by grinding, chemical or mechanicalpolishing (CMP), milling, or other suitable processes used forplanarization. The elongate resilient contact structure 140 shownincludes a single bend region, although multiple bends may be included,as described in U.S. Pat. No. 6,482,013, referenced previously.

In a subsequent step shown in FIG. 1K, the photoresist material 132 isstripped away, exposing ends of the spring contacts 140. The exposedblanket sputtered metal 130 is further removed as shown in FIG. 1Lleaving only the sputtered metal 130 beneath resilient contacts 140.

In a subsequent step illustrated in FIG. 1M, an adhesive material 144,such as epoxy, is applied over an end of the resilient contacts 140 anda portion of the photoresist 120. The adhesive may be filled withparticles for added strength as is known in the art. In a further stepshown in FIG. 1N, a support substrate 150 is applied over the epoxy, andthe epoxy cured. The cured epoxy bonds the support substrate 150 to theresilient contacts 140, as shown in FIG. 1O. In one embodiment, thesupport substrate 150 is a transparent material, such as glass, allowingfor visual alignment of the resilient contacts 140 by looking throughthe transparent substrate when placing it on a space transformersubstrate. The support substrate 150 can likewise be another dielectricmaterial, such as a polymer or a ceramic, or a conductive material suchas metal.

In one embodiment, a conductive metal material 152 can be applied in oneor more regions of the support substrate 150 to form a ground planeunderlying the resilient contacts 140, as illustrated in FIG. 1N. Theground plane 152 serves to provide a capacitive layer beneath theresilient contacts 140, providing for better impedance matching. Sizingof one or more ground plane regions 152 underlying the contact elements140, as well as sizing of the gap width “g” in FIG. 1N can be adjustedfor impedance matching. In one embodiment, the entire support substrate150 can be formed from a conductive metal material with the adhesivematerial 144 forming a non-conductive dielectric electrically isolatingthe support substrate (or ground plane) from the resilient contacts 140.The ground plane can also be formed on the opposite side of supportsubstrate 150.

With the resilient contacts 140 now affixed to the support substrate 150by adhesive 144, in subsequent steps the photoresist material 120 isstripped away, as illustrated in FIG. 1O, and the remaining blanketsputter metal 130 separating the sacrificial substrate 102 is etchedaway along with the sacrificial substrate 102, as illustrated in FIG.1P.

FIGS. 1A-1P describe an exemplary process for fabricating elongatedresilient (spring) interconnection (contact) elements on a supportsubstrate. This can be considered to be an “interim” product, availablefor further use as described to follow.

The support substrate 150 with contact structures 140, as formed inFIGS. 1A-1P, in one embodiment is glued or bonded to a further substrate160 containing electrical routing lines 161, as shown in FIG. 2. Thecontact structures 140 are then connected by wire bonds 162 to contactto bond pads 163 connecting to routing lines 161 in the substrate 160.In one embodiment, the ground plane regions 152 are further connected byone or more wire bonds 164 to a ground connection line 165 providedthrough the substrate 160. With the substrate 160 providing electricalrouting from wire bond pads 163 through routing lines 161 to contacts atanother pitch on an opposing surface of substrate 160, the substrate 160effectively forms a “space transformer” substrate. Although shownmounted on a space transformer substrate 160, the substrate 160 can takeother forms, such as a substrate with routing lines only on its surface,or a substrate with through line vias not providing any “spacetransformation.” The substrate 160 can be formed from a multilayerceramic material, a polymer material effectively forming a PCB, or othermaterial as would be deemed suitable to a person of ordinary skill. Forconvenience, further reference to a substrate, such as substrate 160,attaching to a resilient contact support substrate, such as supportsubstrate 150, will be referred to as a “space transformer substrate.”

FIG. 3 shows another configuration for mounting to a space transformersubstrate 160, where the support substrate 151 is modified to containsvias 172. The vias 172 provide conductive lines from bond pads 177 onthe surface of the support substrate 151 to solder bumps 174 provided onan opposing side of the support substrate 151. The solder bumps 174 canserve to connect the support substrate 151 to the space transformersubstrate 160. Alternatively, in addition to the solder bumps 174, anadhesive fill material such as epoxy or underfill as known in the art(not shown) is further provided between the support substrate 151 andspace transformer substrate 160 to connect the substrates. The solderbumps 174 connect the vias 172 to electrical routing lines 161 withinthe space transformer substrate 160. Opposing ends of the vias 172include bumps or bond pads 177 that are then connected by wire bonds 175to the contact structures 140. One or more additional vias 173 can beprovided to connect the ground planes regions 152 to ground lines 161within the space transformer substrate 160.

FIG. 4 shows another configuration for mounting where resilient springs200 are provided between the support substrate 150 and a printed circuitboard (PCB) 165. By being mounted on resilient springs 200, the supportstructure 150 forms a compliant platform for testing components on awafer, the compliant nature limiting the possibility of damaging thewafer or the components formed thereon during test probing. Theresilient springs 200 can be a metal coil spring as shown, an elongatedspring similar to the resilient contacts 140, a spring structure madefrom a resilient elastomer or flexible material such as rubber, or otherresilient material as known in the art. Flexible conductive connections202 connect the PCB 165 to the resilient contacts 140. The flexibleconnections 202 are shown in FIG. 4 to be bonded to pads 204 on thesupport structure 150, and to a socket 206 or other flex connection onthe PCB substrate 165. The flexible connections 202 are connected to thebond pad 204 and socket 206 using thermosonic compression, or otherbonding procedures known in the art. Wire bonds 175 connect theresilient contacts 140 to the bond pad 204. Routing lines within thespace transformer PCB 165 (not shown) connect the flex connection 202 toconnectors 208 on the opposing side of the PCB 165 for connecting to awafer tester.

FIG. 5 shows modification to the compliant platform configuration ofFIG. 4 so that the resilient contacts 140 are connected by the flexibleconnections 202 directly to the pad 206 on the PCB substrate 165 withoutusing a separate wire bond 175. The structure of FIG. 5 may be useful tosimplify manufacturing if the flexible connections do not place asignificant amount of force on the resilient contacts 140, or if betterelectrical properties are obtained by having a shorter electrical pathfrom the resilient contacts 140 to the PCB substrate 165.

FIG. 6 shows another configuration where resilient contacts 140 areprovided on a transparent support substrate 150 and mounted on a PCB165, the PCB 165 having one or more openings 210 allowing light to passthrough the transparent support substrate 150 to enable testing of lightsensitive devices. The substrate 150 can be attached to the PCB 165using an adhesive, such as epoxy similar to adhesive material 144, orusing resilient springs to form a compliant platform as in FIGS. 4-5.The configuration of FIG. 6 is shown provided over a wafer 212, with theresilient contacts 140 aligned for probing pads 214 on the wafer 212 totest ICs on the wafer. Signals to and from the resilient contacts 140are provided through connectors 208 to a tester as shown in FIGS. 4-5.The wafer 212 is further shown with light sensitive devices 216, such ascharge coupled devices (CCDs), image sensors for cell phones withcameras, or similar optical components that are light sensitive. A lightsource 218, such as a laser or light emitting diode, is shown providedover the test structure. Light emitted from source 218 is providedthrough an opening 210 in the PCB 165, and through the transparentsupport substrate 150 to provide signals to the light sensitivecomponents 216 on the wafer 212 for testing. Testing of optical andelectrical components on the wafer 212 can, thus, be done concurrently.

FIG. 7 shows a top view of resilient contact structures 140 on thesupport substrate 150, as set to contact one configuration of pads on asingle DUT. In FIG. 7, wire bonding is provided from the resilientcontact structures 140 to bond pads 163 on a space transformer substrate160, similar to the configuration shown in cross-section in FIG. 2. Theresilient contact structures 140 are arranged on the support substrate150 so that tips 180 (formed in intrusions 110 shown in FIG. 1D-1) areprovided over the DUT contacts pads (not shown). Dashed lines illustratethe peripheral area of a DUT, with one configuration of pads arrangedaround the periphery of the DUT. Wire bonds 162 connect the contactstructures 140 to contact pads 163 on the space transformer substrate160. A further wire bond 164 connects a ground plane on the surface ofsupport substrate 150 to a ground line contact pad 178 on the spacetransformer substrate 160. The wire bond 164 leading to ground is placedin close proximity to signal lines for good signal fidelity. Althoughonly a single ground line 164 is shown, additional lines can be providedto improve signal fidelity. In FIG. 7, it is assumed that a ground planeis provided over the entire surface of the support substrate 150,however, individual ground plane regions underlying one or more of thecontact structures 140 might alternatively be used. The non-conductiveadhesive material 144 separates the ground plane region from the contactstructures 140. The contact pads 163 and 178, in one embodiment, areassumed connected to internal lines in the space transformer 160,similar to the arrangement of lines illustrated in FIG. 2.

FIG. 8 shows a top view of resilient contact structures 140 on a supportsubstrate 151 alternatively having pads and vias for connecting to aspace transformer substrate 166, similar to the arrangement of FIG. 3.The signal vias are terminated into pads 177 on the substrate 151. Theground plane region 152 on the support substrate 151 then has openings153 to electrically isolate the signal pads 177 connecting to vias.Although the ground plane region 152 is shown surrounding the signalpads 177, as an alternative, the signal pads 177 could be providedoutside a ground plane region on the support substrate 151. The groundplane regions 152 are then directly connected by a via 173 to a groundline in the space transformer substrate 160. The contact structures 140are electrically isolated from the ground planes 152 by non-conductiveadhesive material 144. The resilient contact structures 140 areconnected by wire bonds 175 to the bond pads 177. As discussedpreviously, the size of the ground plane region 152 (or regions ifseparate ground planes underlie each contact) can be adjusted to controlthe resulting impedance through the wire bond 175 and contact structure140. In one embodiment, an adhesive material 222 can be dispensed incontinuous beads over a number of probes. As noted previously, theadhesive material 222 is provided to improve the flexural strength, orprevent pealing of the probes 140 from the support substrate 151.Examples of the adhesive material 222 include an epoxy resin, filledepoxy, cyanate ester, BCB or other materials with adhesive propertiesrecognized in the art.

As an alternative to directly wire bonding a resilient contact 140 to apad 177 over a via as shown in FIG. 8, a length of trace 181 can addedas illustrated in FIG. 9. The length of trace 181 connects the bond wire175 to the via 172. The length and size of trace 181 can be adjusted forimproved impedance matching. The trace 181 further can include a thinfilm resistor sized to provide for impedance matching. A higherimpedance can be achieved with the thin film resistor provided in trace181, as opposed to simply adjusting the size of a conductive line makingup trace 181. The thin film resistor could serve as a series element ina conductive line, or as a termination. The trace 181 can also include ahigh frequency capacitor. The capacitor could serve as a descrete serieselement, or could provide a bypass to ground. An alternative to FIG. 9is shown in FIG. 10 with the trace 181 providing a bond pad connection,rather than using a via. As shown in FIG. 10, a first bond wire 194connects the resilient contact 140 to a first end of trace 181, whileanother bond wire 196 connects a second end of the trace 181 to a bondpad 198 on space transformer substrate 160. An internal routing line 197in space transformer substrate 160 connects the bond pad 198 to anopposing side of the substrate 160.

FIG. 11 shows a top view of an alternative configuration to that shownin FIGS. 7 and 8 for the arrangement of resilient contact structures 140on a support substrate 150. As shown, the resilient contact structures140 are rearranged so that tips 180 are aligned over pads arranged alonga centerline of a DUT. The DUT perimeter is illustrated by dashed lines.Although not shown in FIG. 7, wire bonding and ground planes can beprovided as described previously.

FIG. 12 shows a top view of a substrate 150 on which resilient contactstructures are formed illustrating how the substrate 150 can bemanufactured and then diced up to improve manufacturing yield. Theconfiguration shown includes groups of resilient spring contactsconfigured to contact with pads on a DUT having contacts around itsperiphery as illustrated in FIGS. 7 and 8. Twenty-six groups of springcontacts are illustrated as formed on a support substrate 150 having theshape of a wafer. Lines illustrate boundaries of individual ones of thegroups of spring contacts. Cuts can be made along the lines to dice upthe support substrate 150 into twenty-six individual DUT teststructures. The individual support substrate tiles can be tested, eitherbefore or after dicing, and if testing proves a tile is functional, thetile can be attached to a space transformer substrate, as discussedpreviously. By dicing up the support substrate 150 to form individualtiles, and discarding non-functional tiles, manufacturing yield can beimproved.

As an alternative to dicing along the lines shown in FIG. 12, dicing canbe performed to keep two or more of the groups of resilient contactstogether, as illustrated by the larger dashed lines 190. Precisionalignment of the groups of contacts relative to each other can, thus, bemaintained while increased manufacturing yield is still provided withsome groups of four being discarded if they are non-functional.

FIG. 13 shows a cross sectional view of components of a probe cardillustrating flexible mounting of a space transformer substrate 160, asan alternative to the resilient springs 200 used in FIGS. 4-5, toconnect to a PCB 165 containing connectors 203 for connecting to a testsystem controller. The space transformer substrate 160 can be configuredas shown in FIGS. 2-3, or as a system with openings allowing opticalconnections similar to FIG. 6 to be flexibly mounted using the systemshown in FIG. 13. Other configurations, as illustrated in FIGS. 7-11 canlikewise be flexibly mounted as illustrated in FIG. 13.

The probe card of FIG. 13 is shown configured to provide both electricalpathways and mechanical support for the probes 140 that will directlycontact a wafer. FIG. 13 includes a space transformer 160 configured asshown in FIG. 2. The probe card electrical pathways are provided throughthe space transformer 160 as well as a printed circuit board (PCB) 165,and an interposer 232. Test data for a test system controller isprovided through pogo pins or zero insertion force (ZIF) connectors 203connected around the periphery of the PCB 165. Channel transmissionlines 240 distribute signals from the tester interface connectors (pogoor ZIF) 203 horizontally in the PCB 165 to contact pads on the PCB 165to match the routing pitch of pads on the space transformer 160. Theinterposer 232 includes a substrate 42 with spring probe electricalcontacts 44 disposed on both sides. The interposer 232 electricallyconnects individual pads on the PCB 165 to pads forming a land gridarray (LGA) on the space transformer 160. The LGA pad connections aretypically arranged in a regular multi-row pattern. Transmission lines246 in a substrate 45 of the space transformer 160 distribute or “spacetransform” signal lines from the LGA to spring probes 140 configured inan array. The space transformer 160 with embedded circuitry, probes andLGA is referred to as a probe head.

Mechanical support for the electrical components is provided by a backplate 250, bracket 252, frame 254, leaf springs 256, and leveling pins262. The back plate 250 is provided on one side of the PCB 165, whilethe bracket 252 is provided on the other side and attached by screws259. The leaf springs 256 are attached by screws 258 to the bracket 252.The leaf springs 256 extend to movably hold the frame 254 within theinterior walls of the bracket 252. The frame 254 then includeshorizontal extensions 260 for supporting the space transformer 160within its interior walls. The frame 254 surrounds the probe head andmaintains a close tolerance to the bracket 252 such that lateral motionis limited.

Leveling pins 262 complete the mechanical support for the electricalelements and provide for leveling of the space transformer 234. Theleveling pins 262 are adjusted so that brass spheres 266 provide a pointcontact with the space transformer 160. The spheres 266 contact outsidethe periphery of the LGA of the space transformer 160 to maintainisolation from electrical components. Leveling of the substrate isaccomplished by precise adjustment of these spheres through the use ofadvancing screws 262, referred to as the leveling pins. Leveling pins262 are adjustable to level the space transformer 160 and assure all theprobes 140 will make contact with a wafer. The leveling pins 262 arescrewed through supports 265 in the back plate 250. Motion of theleveling pin screws 262 is opposed by leaf springs 256 so that spheres266 are kept in contact with the space transformer 160. The leaf springs256 are designed to be much stronger than the interposer 232, so thatraising and lowering the leveling screws 262 is opposed by the leafsprings 256 and the springs 242 and 244 of the interposer 232 serve onlyto assure electrical contact is maintained between the space transformer160 as it moves relative to the PCB 165.

Although the present invention has been described above withparticularity, this was merely to teach one of ordinary skill in the arthow to make and use the invention. Many additional modifications willfall within the scope of the invention, as that scope is defined by thefollowing claims.

1. A method of forming a contact element on a support substratecomprising: providing a first substrate; forming an intrusion in thefirst substrate, the intrusion for forming a contact tip for the contactelement; applying a first layer of photoresist and patterning thephotoresist to form openings over the intrusion and a region of thefirst 1 substrate adjacent the intrusion; applying a conductive layerover the exposed first substrate and first photoresist layer; applyingand patterning a second layer of photoresist to form openings over aportion of the first photoresist layer and the first substrate separatefrom the intrusion; applying a resilient metal material in openingsformed between regions of the second layer of photoresist and removingthe second layer of photoresist; applying an adhesive material over aportion of the contact element separate from the intrusion; attachingthe support substrate to the adhesive material; removing the firstphotoresist material; and removing the first substrate.
 2. The method ofclaim 1, further comprising: attaching the support substrate to a spacetransformer substrate having bond pads attached to routing lines withinthe space transformer substrate; and wire bonding the contact element toone of the bond pads.
 3. The method of claim 2, further comprising:applying a metal ground plane region to the support substrate prior toattaching the support substrate to the contact element using theadhesive, wherein the adhesive is non-conductive to isolate the contactelement from the ground plane region.
 4. The method of claim 3, furthercomprising: wire bonding the ground plane to one of the bond pads.